AB1658 COMPARISON OF STERNOCLEIDOMASTOIDEUS FLEXIBILITY, VAGUS NERVE FUNCTION, AND GASTROINTESTINAL SYMPTOMS IN CHRONIC NECK PAIN AND HEALTHY INDIVIDUALS
Authors: Y. Özel Asliyüce, Ö. Uysal, A. Fanuscu, U. Berberoğlu, O. Ulger
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> The vagus nerve emerges from the jugular foramen and continues through the carotid sheath in the cervical region. The carotid sheath is in contact with the SCM muscle. It has been hypothesized that Sternokleidomastoideus (SCM) muscle tension may affect the carotid sheath and the function of the vagus nerve passing through it. It is known that there is an increase in activation of the SCM muscle in individuals with chronic neck pain (CNP), which may change the passive mechanical properties of the muscle [1]. It has been shown that vagus nerve dysfunction can cause pathologies in the organs it innervates. Although the relationship between vagal dysfunction and gastrointestinal system symptoms is clear, the mechanisms that may affect vagus nerve function have not yet been clarified. <h3>Objectives</h3> This study aims to compare the passive mechanical properties of the SCM muscle, vagus nerve function, and gastrointestinal symptoms in healthy individuals with neck pain. <h3>Methods</h3> Tone, stiffness and elasticity, which are the passive mechanical properties of the SCM muscle, were measured with the Myoton-3 myotonometric medical device (Muomeetria AS, Estonia, EU). Vagus nerve function was evaluated with the Vagus Neurodynamic Test (VAGUS-NDT)[2]. The test was performed bilaterally. Gastrointestinal symptoms were evaluated with the Gastrointestinal Symptom Rating Scale (GSRS). <h3>Results</h3> 29 individuals, 15 healthy, 14 with CNP, who were not diagnosed with gastrointestinal or any systemic disease were included in the study. In individuals with CNP, the positivity of VAGUS-NDI test and GSRS all sub-scores (reflux, indigestion, diarrhea, constipation and abdominal pain) and total score were higher than healthy individuals (p&lt;0.05). In addition, right and left elasticity scores for the SCM muscle were lower in these individuals than in healthy individuals (p&lt;0.05) while tone and stiffness were similar(p&gt;0.05). <h3>Conclusion</h3> According to our preliminary results, SCM elasticity was lower and the incidence of vagal dysfunction and gastrointestinal symptoms were higher in individuals with CNP than in healthy. This may be due to compression of the vagus nerve passing through the carotid sheath as a result of decreased SCM muscle elasticity. The increase in the tension of the soft tissues around a nerve in the body restricts the movement of the nerve, affecting its function and making it susceptible to entrapment. Even this slight nerve compression can cause entrapment and lead to neuroinflammation[3]. This research is a preliminary conclusion that neck pain and decreased SCM elasticity may be an important factor that may affect vagal function. This relationship needs to be investigated with a larger sample group and advanced statistical methods. <h3>References</h3> [1]Wolff, W.L., C.M. Heinemann, and D.B. Lipps, The influence of idiopathic chronic neck pain on upper trapezius and sternocleidomastoid muscle activity and elasticity during functional reaching: A cross-sectional study. Journal of Biomechanics, 2022. 141: p. 111223. [2]Carta, G., et al., Discovering the Vagus: Validation and Inter-Rater Reliability of the Vagus Nerve Neurodynamic Test Among Healthy Subjects. Available at SSRN 3529450, 2020. [3]Menorca, R.M., T.S. Fussell, and J.C. Elfar, Nerve physiology: mechanisms of injury and recovery. Hand Clin, 2013. 29(3): p. 317-30. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.